Lavrov I, Gerasimenko Y, Burdick J, Zhong H, Roy R R, Edgerton V R
Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia; and
Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Pavlov Institute of Physiology, St. Petersburg, Russia; Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia; and.
J Neurophysiol. 2015 Dec;114(6):3306-14. doi: 10.1152/jn.00583.2015. Epub 2015 Oct 7.
In this study we investigated the ability of sensory input to produce tonic responses in hindlimb muscles to facilitate standing in adult spinal rats and tested two hypotheses: 1) whether the spinal neural networks below a complete spinal cord transection can produce tonic reactions by activating different sensory inputs and 2) whether facilitation of tonic and rhythmic responses via activation of afferents and with spinal cord stimulation could engage similar neuronal mechanisms. We used a dynamically controlled platform to generate vibration during weight bearing, epidural stimulation (at spinal cord level S1), and/or tail pinching to determine the postural control responses that can be generated by the lumbosacral spinal cord. We observed that a combination of platform displacement, epidural stimulation, and tail pinching produces a cumulative effect that progressively enhances tonic responses in the hindlimbs. Tonic responses produced by epidural stimulation alone during standing were represented mainly by monosynaptic responses, whereas the combination of epidural stimulation and tail pinching during standing or epidural stimulation during stepping on a treadmill facilitated bilaterally both monosynaptic and polysynaptic responses. The results demonstrate that tonic muscle activity after complete spinal cord injury can be facilitated by activation of specific combinations of afferent inputs associated with load-bearing proprioception and cutaneous input in the presence of epidural stimulation and indicate that whether activation of tonic or rhythmic responses is generated depends on the specific combinations of sources and types of afferents activated in the hindlimb muscles.
在本研究中，我们调查了感觉输入在成年脊髓损伤大鼠后肢肌肉中产生紧张性反应以促进站立的能力，并测试了两个假设：1）完全脊髓横断以下的脊髓神经网络是否能通过激活不同的感觉输入产生紧张性反应；2）通过激活传入神经和脊髓刺激来促进紧张性和节律性反应是否涉及相似的神经元机制。我们使用一个动态控制平台在负重过程中产生振动、进行硬膜外刺激（在脊髓S1水平）和/或夹尾，以确定腰骶脊髓能产生的姿势控制反应。我们观察到平台位移、硬膜外刺激和夹尾的组合产生了累积效应，逐渐增强后肢的紧张性反应。站立时单独硬膜外刺激产生的紧张性反应主要由单突触反应表示，而站立时硬膜外刺激和夹尾的组合或在跑步机上行走时的硬膜外刺激促进了双侧的单突触和多突触反应。结果表明，在硬膜外刺激存在的情况下，通过激活与负重本体感觉和皮肤输入相关的特定传入输入组合，可以促进完全脊髓损伤后的紧张性肌肉活动，并表明紧张性或节律性反应的产生取决于后肢肌肉中激活的传入神经来源和类型的特定组合。
